So I have tested these both quite extensively and notice no significant difference...

Both have same amount of stamina reduction so no difference there. Craft Speed is slightly better on the steel anvil (no biggie as late game crafts take so much stamina the speed isnt what caps you its the stamina drain)

Quality of the hammer had pretty much no effect on the outcome, did 30 iron pickaxe crafts each hammer using 3 diff iron hammers 82%, 103%, 122%. The avg quality were 101% with the 82%, 99% with the 103%, and 102% with the 122% Iron hammer.

Tested all the variables I could think of to ensure accurate testing.

*****Repeated the test again crafting Bronze Hammers this time (much lower skill lvl) using the same 122% iron hammer. Sample size was 50 hammers each anvil.

@KhaosArrow Ty for info. Before steam release anvil effected speed only. Then it should be fixed to give bonus to quality of item's crafted but seems it's not working right. Or works like Korean random ) Need to check it. then send report to devs.

@StephenHawkings Well there are 2 ways how to make it useful. First way is to make it as requirement for steel items crafting. Second – make it affect craft quality. Second thing must be implemented for all other things working same way like workbench but we don’t have different work benches. As well as we need to make it same for bronze in crucible or refining forge. Not really sure which way is the right one.